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Article: Ultra‐low‐field magnetization transfer imaging at 0.055T with low specific absorption rate

TitleUltra‐low‐field magnetization transfer imaging at 0.055T with low specific absorption rate
Authors
Keywordsbrain
magnetization transfer
MRI
specific absorption rate
tissue contrast
ultra-low-field
Issue Date24-Jul-2024
PublisherWiley
Citation
Magnetic Resonance in Medicine, 2024 How to Cite?
Abstract

Purpose: To demonstrate magnetization transfer (MT) effects with low specific absorption rate (SAR) on ultra-low-field (ULF) MRI. Methods: MT imaging was implemented by using sinc-modulated RF pulse train (SPT) modules to provide bilateral off-resonance irradiation. They were incorporated into 3D gradient echo (GRE) and fast spin echo (FSE) protocols on a shielding-free 0.055T head scanner. MT effects were first verified using phantoms. Brain MT imaging was conducted in both healthy subjects and patients. Results: MT effects were clearly observed in phantoms using six SPT modules with total flip angle 3600° at central primary saturation bands of approximate offset ±786 Hz, even in the presence of large relative B0 inhomogeneity. For brain, strong MT effects were observed in gray matter, white matter, and muscle in 3D GRE and FSE imaging using six and sixteen SPT modules with total flip angle 3600° and 9600°, respectively. Fat, cerebrospinal fluid, and blood exhibited relatively weak MT effects. MT preparation enhanced tissue contrasts in T2-weighted and FLAIR-like images, and improved brain lesion delineation. The estimated MT SAR was 0.0024 and 0.0008 W/kg for two protocols, respectively, which is far below the US Food and Drug Administration (FDA) limit of 3.0 W/kg. Conclusion: Robust MT effects can be readily obtained at ULF with extremely low SAR, despite poor relative B0 homogeneity in ppm. This unique advantage enables flexible MT pulse design and implementation on low-cost ULF MRI platforms to achieve strong MT effects in brain and beyond, potentially augmenting their clinical utility in the future. 


Persistent Identifierhttp://hdl.handle.net/10722/351813
ISSN
2023 Impact Factor: 3.0
2023 SCImago Journal Rankings: 1.343

 

DC FieldValueLanguage
dc.contributor.authorSu, Shi-
dc.contributor.authorZhao, Yujiao-
dc.contributor.authorDing, Ye-
dc.contributor.authorLau, Vick Man Hin-
dc.contributor.authorXiao, Linfang-
dc.contributor.authorLeung, Gilberto K. K.-
dc.contributor.authorLau, Gary K. K.-
dc.contributor.authorHuang, Fan-
dc.contributor.authorVardhanabhuti, Vince-
dc.contributor.authorLeong, Alex T. L.-
dc.contributor.authorWu, Ed Xuekui-
dc.date.accessioned2024-12-01T00:35:10Z-
dc.date.available2024-12-01T00:35:10Z-
dc.date.issued2024-07-24-
dc.identifier.citationMagnetic Resonance in Medicine, 2024-
dc.identifier.issn0740-3194-
dc.identifier.urihttp://hdl.handle.net/10722/351813-
dc.description.abstract<p> <span>Purpose: To demonstrate magnetization transfer (MT) effects with low specific absorption rate (SAR) on ultra-low-field (ULF) MRI. Methods: MT imaging was implemented by using sinc-modulated RF pulse train (SPT) modules to provide bilateral off-resonance irradiation. They were incorporated into 3D gradient echo (GRE) and fast spin echo (FSE) protocols on a shielding-free 0.055T head scanner. MT effects were first verified using phantoms. Brain MT imaging was conducted in both healthy subjects and patients. Results: MT effects were clearly observed in phantoms using six SPT modules with total flip angle 3600° at central primary saturation bands of approximate offset ±786 Hz, even in the presence of large relative B</span><sub>0</sub><span> inhomogeneity. For brain, strong MT effects were observed in gray matter, white matter, and muscle in 3D GRE and FSE imaging using six and sixteen SPT modules with total flip angle 3600° and 9600°, respectively. Fat, cerebrospinal fluid, and blood exhibited relatively weak MT effects. MT preparation enhanced tissue contrasts in T2-weighted and FLAIR-like images, and improved brain lesion delineation. The estimated MT SAR was 0.0024 and 0.0008 W/kg for two protocols, respectively, which is far below the US Food and Drug Administration (FDA) limit of 3.0 W/kg. Conclusion: Robust MT effects can be readily obtained at ULF with extremely low SAR, despite poor relative B</span><sub>0</sub><span> homogeneity in ppm. This unique advantage enables flexible MT pulse design and implementation on low-cost ULF MRI platforms to achieve strong MT effects in brain and beyond, potentially augmenting their clinical utility in the future. </span> <br></p>-
dc.languageeng-
dc.publisherWiley-
dc.relation.ispartofMagnetic Resonance in Medicine-
dc.rightsThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.-
dc.subjectbrain-
dc.subjectmagnetization transfer-
dc.subjectMRI-
dc.subjectspecific absorption rate-
dc.subjecttissue contrast-
dc.subjectultra-low-field-
dc.titleUltra‐low‐field magnetization transfer imaging at 0.055T with low specific absorption rate-
dc.typeArticle-
dc.identifier.doi10.1002/mrm.30231-
dc.identifier.scopuseid_2-s2.0-85199363621-
dc.identifier.eissn1522-2594-
dc.identifier.issnl0740-3194-

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